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#!/usr/bin/env python
# encoding: utf-8
'''
Simple Chunk Cross-Over Replacement Module for AFLFuzz
@author: Christian Holler (:decoder)
@license:
This Source Code Form is subject to the terms of the Mozilla Public
License, v. 2.0. If a copy of the MPL was not distributed with this
file, You can obtain one at http://mozilla.org/MPL/2.0/.
@contact: choller@mozilla.com
'''
import random
def init(seed):
'''
Called once when AFLFuzz starts up. Used to seed our RNG.
@type seed: int
@param seed: A 32-bit random value
'''
# Seed our RNG
random.seed(seed)
def fuzz(buf, add_buf, max_size):
'''
Called per fuzzing iteration.
@type buf: bytearray
@param buf: The buffer that should be mutated.
@type add_buf: bytearray
@param add_buf: A second buffer that can be used as mutation source.
@type max_size: int
@param max_size: Maximum size of the mutated output. The mutation must not
produce data larger than max_size.
@rtype: bytearray
@return: A new bytearray containing the mutated data
'''
# Make a copy of our input buffer for returning
ret = bytearray(buf)
# Take a random fragment length between 2 and 32 (or less if add_buf is shorter)
fragment_len = random.randint(1, min(len(add_buf), 32))
# Determine a random source index where to take the data chunk from
rand_src_idx = random.randint(0, len(add_buf) - fragment_len)
# Determine a random destination index where to put the data chunk
rand_dst_idx = random.randint(0, len(buf))
# Make the chunk replacement
ret[rand_dst_idx:rand_dst_idx + fragment_len] = add_buf[rand_src_idx:rand_src_idx + fragment_len]
# Return data
return ret
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